Calculators
Over-Refraction Calculator
Final lens prescription from current lens, rotation on eye and refraction over lens
1 Current Lens Prescription
2 Lens Rotation on Eye
Direction is described from the practitioner's view at the slit-lamp (LARS: Left Add / Right Subtract). Lens rotates left = counter-clockwise; lens rotates right = clockwise.
3 Refraction Over Lens (ROL)
Final Lens Power to Order
New Lens Rx
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Sphere
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Cylinder
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Axis
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How this calculator works
- The current lens cylinder axis is rotated by the observed on-eye rotation (using the selected direction) to find where the cylinder actually sits on the eye.
- Both prescriptions (rotated lens + over-refraction) are converted to Long/Thibos power vectors (M, J₀, J₄₅).
- The vectors are summed to produce the combined prescription on the eye.
- The combined vector is converted back to sphero-cylinder form (negative-cylinder).
- The resulting axis is de-rotated back to the lens reference frame to give the prescription to ORDER.
- Sphere and cylinder are rounded to the nearest 0.25 D, axis to the nearest 1°.
“Deze tool is uitsluitend bedoeld als klinisch hulpmiddel. De uiteindelijke beslissing over het parameters blijft de verantwoordelijkheid van de aanpasser.”